Drying installation

ABSTRACT

An installation for the drying by atomization of products dissolved or suspended in a liquid, comprising a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber, and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air. The drying chamber is provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber, and at least one discharge aperture for the discharge of the drying air and of the portion of the powder entrained by the latter. The discharge aperture communicates with an air powder separator.

United States Patent [1 1 Laguilharre DRYING INSTALLATION [76] Inventor: Pierre Robert Laguilharre, 6 rue Robin, Enghien-Les-Bains, France [22] Filed: Feb. 1, 1971 [2]] Appl. No.: 111,298

[30] Foreign Application Priority Data Feb. 20, 1970 France 7006095 [52] US. Cl 34/57 E, 159/4 R [51] Int. Cl. F26b 17/10 [58] Field of Search 34/57 E, 10;

[56] References Cited UNITED STATES PATENTS 2,911,036 l1/1959 Lazar et a] 159/4 2,154,000 4/1939 Zizinia et al. 334/10 X 3,600,817 8/1971 Klein 34/57 E 3,494,047 2/1970 Geiger et al. 34/10 2,702,949 3/1955 Parker, Jr 34/57 E June 26, 1973 2,240,854 5/1941 Pebbles 34/57 E 1,829,477 10/1931 Douthitt 34/57 E Primary Examiner-Meyer Perlin Assistant Examiner-William C. Anderson Attorney-Woodhams, Blanchard and Flynn [57] ABSTRACT An installation for the drying by atomization of products dissolved or suspended in a liquid, comprising a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber, atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air. The drying chamber is provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber, and at least one discharge aperture for the discharge of the drying air and of the portion of the powder entrained by the latter. The discharge aperture communicates with an air powder separator.

22 Claims, 11 Drawing Figures PATENIEUJUHZG 1975 3. 740.865

sum 1 or 5 I v DRYING INSTALLATION The present invention relates to an installation for the drying by atomization of products dissolved or suspended in a liquid comprising a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air, the drying chamber being provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber and at least one discharge aperture for the discharge of the drying air and of the portion of powder entrained by the latter, said at least one discharge aperture communicating with an air/powder separator.

It is well known that drying chambers as defined above which are, for example, used for drying milk products and called two-outlet chambers" offer the advantage over so-called one-outlet chambers, in which the drying air and the powder formed are discharged through the same orifice, of passing only a small amount of powder into the air-powder separator. Better separation of air and powder is thus achieved and problems of clogging do not occur.

However, in the case of two-outlet drying chambers the need to collect the powder at two separate points, namely at the outlet of the drying chamber and at the outlet of the air-powder separator, entails a certain number of problems which up to the present time have not been satisfactorily solved. The aim of the present invention is to provide an atomization drying installation containing a drying chamber of this type which permits simple collection of the powder produced.

For this purpose,-the installation is characterized by the fact that the air/powder separator is a double-flow, air/powder separator which is arranged adjacent the drying chamber and provided with a powder outlet leading into the interior of the drying chamber and at least one auxiliary air injection device for injecting auxiliary air into the interior of the said separator and towards the said chamber, the direction of air flowing through the said at least one injection device being the resultant of an axial component and of a tangential component.

Thus, the totality of the powder is evacuated by the discharge means provided in the drying chamber, whereas the air/powder separator receives only a reduced quantity of powder.

Such an installation can be made particularly compact because in a double-flow separator, the inlet of the gas mixed with a fraction of powder and the outlet of the powder separated from the air are situated at the same endthereof.

The drying chamber is preferably substantially cylindrical and the double-flow separator is juxtaposed coaxially to said chamber.

Owing to this dispositiomthe current of auxiliary air which passes from the double-flow separator into the drying chamber through the powder outlet communicates, at the base of said chamber, its helicoidal movement to the drying air and to the particles of powder which it contains. Under the action of centrifugal force a substantial proportion of these particles is thrown in the direction of the walls of the drying chamber, thus being separated from the current of drying air before the latter passes into the double-flow separator.

It is advantageous for the drying chamber to be provided with at least one secondary air admission device, for directing into the interior of the drying chamber, a current of secondary air, the direction of which has an axial component, the axial components of the secondary air in the drying chamber and of the auxiliary air in the separator being directed one towards the other.

The current of secondary air causes the powder to be driven from the walls and towards the discharge means. It is preferable that the at least one secondary air admission device is arranged so that, in operation, the secondary air admitted into the drying chamber also has a tangential component, the tangential components of the secondary air in the drying chamber and of the auxiliary air in the separator being in the same direction.

Thus the secondary air in the drying chamber and the auxiliary air in the double-flow separator, which meet one another at the level where the separator is adjacent to the drying chamber, have both a helicoidal movement.

In the drying chamber, the secondary air communicates its helicoidal movement to the drying air and to the particles of powder which said air contains, said particles being projected towards the walls of the chamber under the action of centrifugal force. This disposition contributes thus to eliminate from the drying air a portion of the powder carried by said air before the latter passes into the double-flow separator.

The temperature of the secondary air admitted into the drying chamber can be selected in dependence on the desired effect. For example, it may be such that the secondary air partly effects the drying of the powder which is formed in said chamber.

Furthermore, when the powder fraction which passes into the separator must be subjected to a particular treatment, such as double drying the principle of which is described in French Pat. Application No. 69,33065 or to insantisation" treatment, it is advantageous for the double-flow separator to be provided with a plurality of auxiliary air injection devices arranged to be fed with air at different temperatures and/or with different humidity contents.

In a preferred embodiment the drying chamber is provided at its portion adjacent to the double-flow separator with a widened portion in which all the powder produced collects and on the periphery of which a powder discharge aperture is provided.

The presence of the widened portion has the particular efiect of preventing the powder brought into the drying chamber by the double-flow separator from sticking to the side walls of said chamber because of their closeness to the powder outlet of the separator, thereby clogging said powder outlet.

In a general way the powder outlet of the separator leading into the drying chamber is constituted by an annular space formed around a diaphragm through which a pipe passes for the passage into the separator of drying air coming from the drying chamber.

It may be desirable to modify the dimensions of the powder outlet of the separator as regards to the working conditions choosen. For this purpose, there can be used either diaphragms having different diameters or diaphragms being movable axially.

Owing to this disposition, the diaphragm may be located at the level of the wall of the drying chamber adjacent to the double-flow separator or above said wall,

the size of the powder outlet increasing in proporn'on as the diaphragm moves away from said wall. When the diaphragm is movable axially, its diameter may be slightly greater than that of the separator, so that the dimensions of the powder outlet vary between a zero value and a maximum value depending on the movement of the diaphragm.

The drying chamber may be horizontal, vertical or inclined.

When the chamber is horizontal or slightly inclined its section is preferably substantially ovoid, the bottom of said chamber forming a spout in which the discharge means are disposed.

When the drying chamber is provided with the widened portion referred to above, only the section of said widened portion may be substantially ovoid, the bot tom of said widened portion constituting an extraction hopper.

In the case of substantially vertical chamber, the discharge aperture communicating with the double-flow separator is surmounted by a removable deflector.

This deflector prevents the powder which falls on the bottom of the chamber from being deposited on the diaphragm.

The bottom of the drying chamber may be in the form of a volute, the widened end of which leads into the powder discharge means.

Owing to the helicoidal movement that the auxiliary air from the separator and the secondary air, if any, injected in the drying chamber communicate to the powder, said powder can be evacuated along the volute to the discharge means, where discharge is effected by gravity.

Alternatively, the bottom of the chamber may be movable about its axis. The surface of the" bottom thus covered with powder moves past endlessly under the mouth of a suction device, so that said powder is drawn off and discharged. As an alternative to the suction device a fixed scraper could be used to divert the powder to a discharge aperture.

Finally, with the object of monitoring the conditions of operation of the installation, the latter is preferably provided with a differential measuring device, for measuring the pressure differential in the adjacent zones of the double-flow separator and of the drying chamber. This measuring means may be associated with regulating means for regulating the flow of air passing from the double-flow separator into the drying chamber said regulating means acting either on the flow of auxiliary air injected into the double-flow separator or on the flow of secondary air admitted into the drying chamber, or on both, or else to vary the position of the diaphragm in relation to the wall of the drying chamber adjacent to the double-flow separator when said diaphragm is movable axially.

A number of forms of construction of the installation according to the invention are illustrated, merely by way of example, in the accompanying drawings, in which:

FIG. 1 is a diagrammatical longitudinal section of an installation in which the drying chamber is vertical;

FIG. 2 is a section along the line Il-II of FIG. 1;

FIG. 3 is a section along the line III-III in FIG. 1;

FIG. 4 is a modification of FIG. 1 in which the diaphragm is movable axially;

FIG. 5 is a diagrammatical longitudinal section of an installation in which the drying chamber is horizontal and of substantially ovoid section;

FIG. 6 is a section along the line VI-Vl in FIG. 5;

FIG. 7 is a diagrammatical longitudinal section of an installation in which the drying chamber, which is horizontal, is provided with a widening of substantially ovoid section;

FIG. 8 is a section along the line VIIIVIII in FIG.

FIG. 9 is a diagrammatical longitudinal section of an installation in which the drying chamber is vertical and in which the double-flow separator is fed by two different auxiliary air sources;

FIG. 10 is a diagrammatical longitudinal section of an installation in which the drying chamber is vertical, the bottom of said chamber forming a volute; and

FIG. 11 is a detail view on a larger scale of a modification of FIG. 10 in which the bottom of the drying chamber is movable about its axis.

The installation illustrated in FIGS. 1, 2 and 3 comprises a drying chamber 1 and a double-flow separator 2.

At its top end the drying chamber 1 is provided with a drying air supply duct 3 and a spray 4 for the liquid to be dried; and at its bottom end the drying chamber is provided with powder discharge means 5 for discharging the powder produced and also an aperture 6 for discharging the drying air.

Secondary air admission devices 7 disposed on the periphery of the drying chamber 1 lead tangentially into the interior of the latter through respective apertures 8. These secondary air admission devices 7 are connected in groups of four to respectives headers 9 supplied with secondary air by respective pipes 10.

The double-flow separator 2 is in turn provided with an inlet 11 for the air which is to be freed of powder, an annular outlet 12 for the powder thus separated, and an outlet 13 for the discharge of the air freed of powder.

Auxiliary air injection devices 14 disposed on the periphery of the double-flow separator 2 lead tangentially into the interior of the latter through respective openings 15. The admission devices 14 receive the auxiliary air from a jacket 16 fed by a pipe 17.

The drying chamber 1 and the double-flow separator 2 are juxtaposed coaxially so that the discharge aperture 6 for the drying air provided in the drying chamber 1 and the inlet 1 l for air to be freed of powder provided in the double-flow separator 2 coincide and the powder outlet 12 of the double-flow separator 2 leads into the drying chamber 1.

As can be seen from FIG. 1, the drying air discharge aperture 6 of the drying chamber 1, the inlet 11 for air to be freed of powder in the separator 2 and the powder outlet 12 of said separator are in the form of a diaphragm 18 through which a pipe or sleeve 19 passes. The zone of the drying chamber 1 adjacent to the double-flow separator has a widened portion 20.

The admission devices 7 for admission of secondary air and the injection devices 14 for the injection of auxiliary air are directed in such a manner that the direction of the currents of secondary air and auxiliary air is the resultant of an axial component and of a tangential component, the axial components being directed towards one another and the tangential components being in the same direction.

A differential measuring device 21 is connected rethe double-flow separator 2 and of the drying chamber 1.

The operation of the installation will now be described.

The liquid to be dried is atomized into the drying chamber 1 by the nozzles 4 and is dried by the drying air coming from the duct 3. The secondary air, admitted into the interior of the drying chamber 1 by the admission devices 7 fed by the headers 9 and the pipes 10, penetrates into said drying chamber 1 through the openings 8 in a direction which is the resultant of an axial component and a tangential component. Because of the direction of the admission devices 7 the axial component is directed toward the base of the drying chamber 1. The secondary air thus has a downward helicoidal movement.

The secondary air current surrounds the drying air current which carries the particles of powder formed and communicates to it its downward helicoidal movement. Under the action of centrifugal force the particles of powder are thrown in the direction of the walls of the chamber 1, so that the current of drying air is partly freed of powder.

While a considerable fraction of the powder is deposited on the regulating bottom of the drying chamber 1 and is collected at the outlet of the powder discharge means 5, the drying air charged with humidity passes through the discharge aperture 6 into the double-flow separator 2, entraining the other fraction of powder produced.

The auxiliary air, injected into the interior of the double-flow separator 2 through the injection device 14 fed by the jacket 16 and the pipe 17, penetrates into said separator 2 through the openings in a direction which is the resultant of an axial component and a tangential component.

Because of the direction of the injection devices 14, the axial component is directed towards the bottom of the drying chamber 1 and the tangential component is in the same direction as the tangential component of the direction of the secondary air admitted into the drying chamber 1. The auxiliary air therefore has a rising helicoidal movement.

The admission of secondary air into the drying chamber 1 and the injection of auxiliary air into the doubleflow separator 2 thus create two currents of air'performing a helicoidal movement which meet one another at the base of the drying chamber 1.

The auxiliary air injected into the double-flow separator 2 surrounds the current of drying air coming from the drying chamber 1 and maintains the helicoidal movement which the secondary air admitted into the drying chamber had imparted to said drying air. Under the effect of centrifugal force the particles of powder entrained by the drying air into the double-flow separator 2 are thrown towards the wall of said separator 2 in the current of auxiliary air. The drying air is thus freed of the powder which it carried and escapes through the outlets 13 of the separator 2. The displacement of the current of auxiliary air being in the opposite direction to that of the displacement of the current of drying air, the particles of powder collected in the current of auxiliary air are returned to the drying chamber 1 and collected at the outlet of the discharge means 5. The auxiliary air which has penetrated into the drying chamber 1 through the powder outlet 12 returns into the double- I flow separator 2 through the drying air discharge aper ture 6 and escapes from said separator 2 through the outlet 13.

The differential measuring device 21 for measuring the pressure difierential in the adjacent zones of the drying chamber 1 and separator 2 makes it possible to monitor the conditions of operation of the installation.

This measuring device 21 may be associated with regulating means 21a for regulating, via, for example, valves (not shown) the flow of air passing from the double-flow separator 2 into the drying chamber 1 through the powder outlet 12, said regulating means acting on the flow of auxiliary air injected into the double-flow separator 2 or on the flow of secondary air admitted into the drying chamber 1, or on both.

The installation illustrated in FIG. 4 differs from the preceding one only in the form of construction of the diaphragm 18. For this reason the elements composing the installation shown in FIG. 4 are designated by the same references as the corresponding elements of the installation illustrated in FIG. 1.

In the case of FIG. 4, the diaphragm 18 is secured to the sleeve 19 which can slide axially in a ring 23 carried by legs 24, so that the space e contained between said diaphragm l8 and the bottom 25 of the drying chamber 1 can be adjusted as desired. Since the diaphragm 18 has a diameter slightly greater than that of the doubleflow separator 2, the space e may vary between a zero value and a maximum value e which is dependent on the movement of the diaphragm.

Apart from the ability to adjust the space e by axial displacement of the diaphragm 18, the operation of this installation is in every respect identical with that of the preceding installation.

In the case of the installation illustrated in FIG. 4, the regulating means 21a associated with the differential measuring device 21 may vary the flow of air passing from said separator 2 into said chamber 1 through the powder outlet 12 by causing the axial displacement of the diaphragm, by modification of the value of the space e.

The installation illustrated in FIGS. 5 and 6 differs essentially from the preceding ones by the fact that it has a horizontal drying chamber 1 of substantially ovoid section. The elements of which this installation is composed are designated by the same references as the corresponding elements of the installation illustrated in FIG. 1. In this case the drying chamber 1 is provided with secondary air admission devices 7 only along its bottom, which forms a spout, said secondary air admission devices 7 being disposed in such a manner that the direction of the current of secondary air admitted into the drying chamber is the resultant of an axial component and a tangential component, the axial component being mostly greater than the tangential component.

The operation of this installation is identical 'to that of the installation illustrated in FIG. 1, with the exception that the particles of powder naturally have a tendency to collect through gravity in the spout formed by the bottom of the drying chamber 1. It is for that reason that in the drying chamber there is no need to provide a current of secondary air performing an intensive helicoidal movement in order to free the current of drying air of particles of powder entrained by it towards the double-flow separator 2.

In this case it is sufficient for only the base of the chamber l to be fed with a current of secondary air, the direction of which has a sufficiently large axial component to drive the powder deposited in the spout towards the powder discharge means 5.

The installation illustrated in FIGS. 7 and 8 differs from that illustrated in FIG. 1 only by the fact that the drying chamber 1 is horizontal and that the widened portion 20 of the chamber 1 has a substantially ovoid section. The elements of which this installation is composed are designated by the same references as the corresponding element of the installation shown in FIG. 1.

Because the powder particles tend to collect at the base of the drying chamber 1, it is advantageous to arrange the secondary air supply system in such a manner that the admission devices 7 disposed at the bottom part of said drying chamber 1 have a larger flow than that of the admission devices 7 disposed at the top part of said chamber 1. The secondary air admission devices 7 may also have a different direction depending on the position which they occupy on the periphery of the drying chamber 1.

The bottom of the widened portion 20 forms an extraction hopper the outlet of which constitutes the discharge means 5 for the powder.

The operation of the installation illustrated in FIGS. 7 and 8 is identical in all respects with that of the installation shown in FIG. 1.

The installation illustrated in FIG. -9 differs essentially from that illustrated in FIG. 1 by the fact that the injection devices 14a and 14b of the double-flow separator 2 receive the auxiliary air from two separate jackets 16a and 16b which are fed respectively by the pipes 17a and 17b.

The operation of this installation is identical in all respects with that of the installation illustrated in FIG. 1, while in addition the special construction of the double-flow separator 2 makes it possible for the powder fraction passing into said separator to be subjected to a special treatment.

This form of construction in fact makes it possible to feed the auxiliary air injection devices 14a and 14b with air at different temperatures or different degrees of humidity and therefore, for example; to effect double drying of the powder fraction entrained into the doubleflow separator 2 or instantisation treatment.

The installation in FIG. differs from that illustrated in FIG. 1 by the fact that the bottom of the drying chamber 1 is in the form of a volute 26 the widened end of which leads into the powder discharge means 5.

The drying chamber 1 has no secondary air admission device. The sleeve 19 is surrounded by a frustoconical deflector 27 the base of which constitutes the diaphragm 18.

The operation of this installation is substantially identical to that of the installation illustrated in FIG. 1, with the exception that the falling of the particles of powder formed, in the direction of the bottom of the drying chamber, is not influenced by the injection of secondary air. The deflector 27 diverts the particles of powder which it receives towards the wall of the drying chamber 1 thus preventing such particles from being deposited on the diaphragm 18. The current of auxiliary air which passes from the double-flow separator 2 into the drying chamber 1 through the powder outlet 12 communicates, at the base of said chamber 1, its helicoidal movement to the drying air and to the particles of powder which it contains. Under the action of centrifugal force a substantial proportion of these particles is thrown in the direction of the walls of the drying chamber 1, thus being separated from the current of drying air before the latter pass into the double-flow separator 2.

The particles of powder which have not been entrained into the double flow separator 2 perform a helicoidal movement suitable for causing them to travel along the volute 26 towards the powder discharge means 5 where discharge is effected by gravity.

FIG. 11 illustrates a modified construction of the bottom of the drying chamber 1 of the installation illustrated in FIG. 10. In this case the bottom 28 of the drying chamber 1 is independent of said chamber and is movable about its axis on bearings 29. An extension of said chamber engages in the bottom 28 in such a manner as to provide a relative seal in the chamber 1. A suction device 30 leads into the bottom of the chamber.

The operation of this installation is identical to that of the installation illustrated in FIG. 10, with the exception that the powder collects in the movable bottom 28 of the drying chamber 1 instead of collecting in the volute 26. The surface thus covered with powder moves past endlessly under the mouth of the suction device 30, so that said powder is drawn off and discharged.

It should be noted that the installations which have been described above are able to operate in other positions than those shown in the accompanying drawings. In particular, the installations illustrated in FIGS. 1, 4 and 9 could operate in a horizontal or inclined position and the installation illustrated in FIGS. 5 and 7 could operate in an inclined position.

What I claim is:

1. An apparatus for the drying by atomization of a product dissolved or suspended in a liquid comprising means defining a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air, the drying chamber being provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber and at least one discharge aperture separate from said discharge means for the discharge of the drying air and the portion of powder entrained by the latter, said discharge aperture communicating with an air/powder separator means wherein the separator means is a double-flow air/powder separator which is arranged adjacent the drying chamber and provided with a powder discharge outlet leading into the interior of the drying chamber adjacent said other end thereof and at least one auxiliary air injection device for injecting auxiliary air into the interior of the said separator and towards the said chamber, the direction of air flowing through the said injection device being the resultant of an axial component and of a tangential component.

2. An apparatus as claimed in claim 1 wherein the drying chamber is substantially cylindrical and the double-flow separator is juxtaposed coaxially to said chamber.

3. An apparatus as claimed in claim 1 wherein the drying chamber is provided with at least one secondary air admission device for directing into the interior of the drying chamber a current of secondary air, the direction of which has an axial component, the axial components of the secondary air in the drying chamber and of the auxiliary air in the separator being directed one towards the other.

4. An apparatus as claimed in claim 3 wherein at least one secondary air admission device is arranged so that, in operation, the secondary air admitted into the drying chamber also has a tangential component, the tangential components of the secondary air in the drying chamber and of the auxiliary air in the separator being in the same direction.

5. An apparatus as claimed in claim 1 wherein the double-flow separator contains a plurality of auxiliary air injection devices, arranged to be fed with air at different temperatures and/or with different humidity contents.

6. An apparatus as claimed in claim 1 wherein at its part adjacent to the double-flow separator the drying chamber is provided with a widened portion in which all the powder produced collects and on the periphery of which a powder discharge aperture is provided.

7. An apparatus as claimed in claim 1 wherein the powder outlet of the separator leading into the drying chamber is constituted by an annular space formed around a diaphragm through which there passes a pipe for the passage into the separator of the drying air coming from the drying chamber.

8. An apparatus as claimed in claim 7 wherein the diaphragm is situated at the junction between the drying chamber and the separator.

9. An apparatus as claimed in claim 7 wherein the diaphragm is movable axially.

10. An apparatus as claimed in claim 1 wherein the drying chamber is horizontal and of substantially ovoid section, the bottom of said chamber forming a spout in which the discharge means are disposed.

l 1. An apparatus as claimed in claim 10 wherein the drying chamber is horizontal and the section of the widened portion is substantially ovoid, the bottom of said widened portion constituting a powder extraction hopper.

12. An apparatus as claimed in claim 1 wherein the drying chamber is substantially vertical and the discharge aperture communicating with the double-free separator is surmounted by a removable deflector.

13. An apparatus as claimed in claim 1, wherein the drying chamber is substantially vertical and the bottom of the drying chamber forms a volute, a widened end of which leads into the powder discharge means.

14. An apparatus as claimed in claim 1, wherein the drying chamber is substantially vertical and the bottom of said chamber is movable about its axis.

15. An apparatus for the drying by atomization of products dissolved or suspended in a liquid comprising a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air, the drying chamber being provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber and at least one discharge aperture for the discharge of the drying air and the portion of powder entrained by the latter, said at least one discharge aperture communicating with an air/powder separator wherein the separator is a double-flow, air/- powder separator which is arranged adjacent the drying chamber and provided with a powder outlet leading into the interior of the drying chamber and at least one auxiliary air injection device for injecting auxiliary air into the interior of the said separator and towards the said chamber, the direction of air flowing through the said at least one injection device being the resultant of an axial component and of a tangential component, and a differential measuring device for measuring the pressure differential in the adjacent zones of the doubleflow separator and the drying chamber.

16. An apparatus as claimed in claim 15 wherein the measuringdevice is associated with regulating means for regulating the flow of air passing from the doubleflow separator into the drying chamber.

17. An apparatus as claimed in claim 16 wherein the regulating means act on the flow of auxiliary air injected into the double-flow. separator.

18. An apparatus as claimed in claim 16, wherein the regulating means act on the flow of secondary air admitted into the drying chamber.

19. An apparatus as claimed in claim 16, wherein the regulating means vary the position of the diaphragm in relation to the drying chamber wall adjacent the double-flow separator.

20. An apparatus for the drying by atomization of a product dissolved or suspended in a liquid, comprising:

wall means defining a drying chamber;

first inlet means communicating with one end of said drying chamber for supplying drying air into the interior of said chamber;

second inlet means communicating with said one end of said drying chamber for supplying a liquid thereto, said liquid having a product dissolved or suspended therein, said second inlet means having atomizing means associated therewith for atomizing the liquid to be dried and directing the liquid into the flow of drying air;

first outlet means associated with the other end of said drying chamber for permitting the discharge of the portion of the powder which deposits in the chamber;

second outlet means associated with said other end of said drying chamber and separate from said first outlet means for discharging the drying air from said chamber, said drying air having a portion of the powder entrained therein;

a double-flow air/powder separator means disposed adjacent said other end of said drying chamber for receiving the drying air as discharged from said drying chamber and for separating the entrained powder therefrom;

said separator means including third inlet means communicating with said second outlet means for causing the air discharged from said drying chamber to be supplied to one end of the separator chamber as defined by said separator means;

third outlet means associated with said one end of said separator chamber and communicating with said other end of said drying chamber for permitting the powder separated from the drying air within said separator chamber to be supplied to said drying chamber; and

fourth outlet means communicating with said separating chamber for permitting discharge of air therefrom.

21. An apparatus according to claim 20, wherein the drying chamber and the separation chamber are disseparator means includes an air injection device for causing auxiliary air to flow in a helical pattern around and axially of the separator chamber in a direction toward said one end thereof for causing the entrained powder to be separated from said drying air and transported through the third outlet means, and said fourth outlet means being substantially coaxially aligned with the third inlet means and disposed in communication with said other end of said separator chamber for discharging the air therefrom. 

1. An apparatus for the drying by atomization of a product dissolved or suspended in a liquid comprising means defining a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air, the drying chamber being provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber and at least one discharge aperture separate from said discharge means for the discharge of the drying air and the portion of powder entrained by the latter, said discharge aperture communicating with an air/powder separator means wherein the separator means is a double-flow air/powder separator which is arranged adjacent the drying chamber and provided with a powder discharge outlet leading into the interior of the drying chamber adjacent said other end thereof and at least one auxiliary air injection device for injecting auxiliary air into the interior of the said separator and towards the said chamber, the direction of air flowing through the said injection device being the resultant of an axial component and of a tangential component.
 2. An apparatus as claimed in claim 1 wherein the drying chamber is substantially cyLindrical and the double-flow separator is juxtaposed coaxially to said chamber.
 3. An apparatus as claimed in claim 1 wherein the drying chamber is provided with at least one secondary air admission device for directing into the interior of the drying chamber a current of secondary air, the direction of which has an axial component, the axial components of the secondary air in the drying chamber and of the auxiliary air in the separator being directed one towards the other.
 4. An apparatus as claimed in claim 3 wherein at least one secondary air admission device is arranged so that, in operation, the secondary air admitted into the drying chamber also has a tangential component, the tangential components of the secondary air in the drying chamber and of the auxiliary air in the separator being in the same direction.
 5. An apparatus as claimed in claim 1 wherein the double-flow separator contains a plurality of auxiliary air injection devices, arranged to be fed with air at different temperatures and/or with different humidity contents.
 6. An apparatus as claimed in claim 1 wherein at its part adjacent to the double-flow separator the drying chamber is provided with a widened portion in which all the powder produced collects and on the periphery of which a powder discharge aperture is provided.
 7. An apparatus as claimed in claim 1 wherein the powder outlet of the separator leading into the drying chamber is constituted by an annular space formed around a diaphragm through which there passes a pipe for the passage into the separator of the drying air coming from the drying chamber.
 8. An apparatus as claimed in claim 7 wherein the diaphragm is situated at the junction between the drying chamber and the separator.
 9. An apparatus as claimed in claim 7 wherein the diaphragm is movable axially.
 10. An apparatus as claimed in claim 1 wherein the drying chamber is horizontal and of substantially ovoid section, the bottom of said chamber forming a spout in which the discharge means are disposed.
 11. An apparatus as claimed in claim 10 wherein the drying chamber is horizontal and the section of the widened portion is substantially ovoid, the bottom of said widened portion constituting a powder extraction hopper.
 12. An apparatus as claimed in claim 1 wherein the drying chamber is substantially vertical and the discharge aperture communicating with the double-free separator is surmounted by a removable deflector.
 13. An apparatus as claimed in claim 1, wherein the drying chamber is substantially vertical and the bottom of the drying chamber forms a volute, a widened end of which leads into the powder discharge means.
 14. An apparatus as claimed in claim 1, wherein the drying chamber is substantially vertical and the bottom of said chamber is movable about its axis.
 15. An apparatus for the drying by atomization of products dissolved or suspended in a liquid comprising a drying chamber provided at one end with supply means for supplying drying air into the interior of the drying chamber and atomizing means for atomizing the liquid to be dried and directing the aforesaid liquid into the flow of drying air, the drying chamber being provided at the other end with discharge means for the discharge of the portion of powder produced which deposits in the chamber and at least one discharge aperture for the discharge of the drying air and the portion of powder entrained by the latter, said at least one discharge aperture communicating with an air/powder separator wherein the separator is a double-flow, air/powder separator which is arranged adjacent the drying chamber and provided with a powder outlet leading into the interior of the drying chamber and at least one auxiliary air injection device for injecting auxiliary air into the interior of the said separator and towards the said chamber, the direction of air flowing through the said at least one injection device being the resultant of an axial component and of a tangential component, and a differential measuring device for measuring the pressure differential in the adjacent zones of the double-flow separator and the drying chamber.
 16. An apparatus as claimed in claim 15 wherein the measuring device is associated with regulating means for regulating the flow of air passing from the double-flow separator into the drying chamber.
 17. An apparatus as claimed in claim 16 wherein the regulating means act on the flow of auxiliary air injected into the double-flow separator.
 18. An apparatus as claimed in claim 16, wherein the regulating means act on the flow of secondary air admitted into the drying chamber.
 19. An apparatus as claimed in claim 16, wherein the regulating means vary the position of the diaphragm in relation to the drying chamber wall adjacent the double-flow separator.
 20. An apparatus for the drying by atomization of a product dissolved or suspended in a liquid, comprising: wall means defining a drying chamber; first inlet means communicating with one end of said drying chamber for supplying drying air into the interior of said chamber; second inlet means communicating with said one end of said drying chamber for supplying a liquid thereto, said liquid having a product dissolved or suspended therein, said second inlet means having atomizing means associated therewith for atomizing the liquid to be dried and directing the liquid into the flow of drying air; first outlet means associated with the other end of said drying chamber for permitting the discharge of the portion of the powder which deposits in the chamber; second outlet means associated with said other end of said drying chamber and separate from said first outlet means for discharging the drying air from said chamber, said drying air having a portion of the powder entrained therein; a double-flow air/powder separator means disposed adjacent said other end of said drying chamber for receiving the drying air as discharged from said drying chamber and for separating the entrained powder therefrom; said separator means including third inlet means communicating with said second outlet means for causing the air discharged from said drying chamber to be supplied to one end of the separator chamber as defined by said separator means; third outlet means associated with said one end of said separator chamber and communicating with said other end of said drying chamber for permitting the powder separated from the drying air within said separator chamber to be supplied to said drying chamber; and fourth outlet means communicating with said separating chamber for permitting discharge of air therefrom.
 21. An apparatus according to claim 20, wherein the drying chamber and the separation chamber are disposed adjacent and in substantial axial alignment with one another, said second outlet means and said third inlet means being substantially in alignment for permitting the drying air to flow directly from the drying chamber into the separation chamber, and said third outlet means comprising an annular ring-like opening disposed in surrounding relationship to said third inlet means for providing direct communication from said one end of said separation chamber to said other end of said drying chamber in the vicinity of said first outlet means.
 22. An apparatus according to claim 21, wherein said separator means includes an air injection device for causing auxiliary air to flow in a helical pattern around and axially of the separator chamber in a direction toward said one end thereof for causing the entrained powder to be separated from said drying air and transported through the third outlet means, and said fourth outlet means being substantially coaxially aligned with the third inlet means and disposed in communication with said other end of said separator chamber for discharging the air therefrom. 